Dermatitis is a general term used to describe the features of several skin conditions linked by the clinical finding of inflammation in the epidermis (top layer of the skin). In general it may be thought of as the skin’s response to stress or irritants in the environment, and it is not contagious. There are many different types of dermatitis, which are clinically characterized by the presence of redness, scaling, pruritus (itching), swelling, and in severe cases blistering. Each type of dermatitis has an underlying pathophysiologic mechanism, which directs the appropriate therapy. Family practitioners, internists, allergists and dermatologists (a doctor who specializes in skin diseases), commonly diagnose cases of dermatitis based on the appearance and symptoms. In the event that the dermatitis is caused by an environmental allergen, prick testing with dermal needles (by an allergist) or patch testing with epicutaneous (upon the skin) chemicals applied with stickers on the skin may be necessary to determine the causative agents.
Dermatitis occurs in people of all ages and ethnicities. According to the National Institutes of Health, people who live in dry climates or in cities have a higher risk of developing atopic dermatitis. Approximately 20 percent of children suffer from some form of dermatitis, and some of them continue to have this condition as adults.
Atopic dermatitis, often referred to as eczema, has a high prevalence in children, but may occur at any age. It is caused by a combination of genetic and environmental factors, and is often linked with allergies, asthma, and stress. The clinical appearance of atopic dermatitis may vary by the individual; however, the hallmark clinical picture is acute eruptions of erythematous (red), scaled, and pruritic (itching) plaques involving the antecubital fossa (inner arm crease) and popliteal fossa (behind the knee crease). The condition waxes and wanes and may have periods where the skin appears normal. Atopic dermatitis is usually controlled by identifying and avoiding triggers and maintaining the skin barrier with emollient moisturizers. In moderate to severe cases it may be necessary to treat the affected area with topical steroids or immunomodulators, and systemic antihistamines.
Contact dermatitis is the skin’s innate inflammatory reaction to an offending external environmental chemical trigger. There are three main subcategories of contact dermatitis: urticarial, irritant, and allergic.
On the other hand, with contact urticaria, the least common, hives develop by an IgE-mediated immediate type mechanism to chemical triggers such as environmental allergens or certain foods. The classical clinical presentation is characterized by a local tingling sensation and localized redness and swelling. It is usually treated with topical anti-itch creams, oral antihistamines. In moderate to severe cases systemic steroids may be necessary. As this is an immediate type reaction it may develop rapidly. A common example of contact urticaria is the allergic reaction to latex.
In irritant contact dermatitis (ICD), the most common form, irritants penetrate the skin and in doing so may remove the protective oils and moisture from the skin’s outer layer. This results in chemical injury to the superficial layers of the skin with subsequent inflammation. The dermatitis in ICD usually appears within 48 hours of exposure to a caustic chemical and is generally limited to the areas of the skin which was in contact with the irritant. There may be variation in the clinical appearance depending on the strength of the chemical trigger and the strength of the skin barrier to sustain the insult. ICD can be caused by soaps, detergents, and antiperspirant, among others.
Allergic contact dermatitis (ACD) arises when an immune response is triggered in the skin after repeated contact with allergenic substances (such as fragrances and formaldehyde). The ACD-type dermatitis may be confined to the area of the skin that contacts the allergen; however, distant sites of previous exposure may also re-react with repeated exposures.
The best form of treatment for contact dermatitis is to avoid the substance that causes the inflammatory reaction. It might be difficult to determine the exact component of the substance that is causing the reaction. In ACD, patch tests may need to be performed.
Seborrhoeic dermatitis mostly occurs in the hair-bearing and oily areas of the skin, such as the face, scalp, genital area, and trunk. This form of dermatitis is believed to be an inflammatory reaction to a combination of the Malassezia yeast, a normal inhabitant of the skin, and decreased keratolysis (dead cells being removed) of the skin. Seborrhoeic dermatitis usually appears as dry, pink patches with waxy scale. It can be treated with the use sulfa/sulfacetamide washes and lotions, selenium, and zinc-based lotions and shampoos, topical antifungal/yeast agents (such as the azoles), and topical steroids.
Neurodermatitis is a skin condition that is characterized by tremendous pruritus and subsequent excoriation. As is seen with all chronic dermatoses, the skin may increase in thickness and become rough (lichenified) in the affected area. Physicians may use patch testing, skin biopsies, or blood tests to accurately diagnose the condition, and a neurologic cause must be ruled out. Antipruritus medications such as emollients, topical steroids, and antihistamines may be needed.
For prone individuals, lifestyle changes which maintain the skin barrier and include the avoidance of known triggers are paramount to the reduction of flare-ups and alleviation of symptoms.
Skin Diseases (General).
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